Il giorno ven 7 lug 2023 alle ore 09:04 Jan Beulich <jbeul...@suse.com> ha scritto:
> On 07.07.2023 08:50, Simone Ballarin wrote: > > Il giorno gio 6 lug 2023 alle ore 18:22 Jan Beulich <jbeul...@suse.com> > ha > > scritto: > > > >> On 06.07.2023 18:08, Simone Ballarin wrote: > >>> Il giorno gio 6 lug 2023 alle ore 10:26 Jan Beulich <jbeul...@suse.com > > > >> ha > >>> scritto: > >>> > >>>> On 05.07.2023 17:26, Simone Ballarin wrote: > >>>>> --- a/xen/arch/x86/apic.c > >>>>> +++ b/xen/arch/x86/apic.c > >>>>> @@ -1211,7 +1211,7 @@ static void __init calibrate_APIC_clock(void) > >>>>> * Setup the APIC counter to maximum. There is no way the lapic > >>>>> * can underflow in the 100ms detection time frame. > >>>>> */ > >>>>> - __setup_APIC_LVTT(0xffffffff); > >>>>> + __setup_APIC_LVTT(0xffffffffU); > >>>> > >>>> While making the change less mechanical, we want to consider to switch > >>>> to ~0 in this and similar cases. > >>>> > >>> > >>> Changing ~0U is more than not mechanical: it is possibly dangerous. > >>> The resulting value could be different depending on the architecture, > >>> I prefer to not make such kind of changes in a MISRA-related patch. > >> > >> What do you mean by "depending on the architecture", when this is > >> x86-only code _and_ you can check what type parameter the called > >> function has? > > > > Ok, I will change these literals in ~0U in the next submission. > > Except that I specifically meant ~0, not ~0U. We mean "maximum value" > here, and at the call site it doesn't matter how wide the function > parameter's type is. If it was 64-bit, ~0U would not do what is wanted. > > Jan > ~0 is not a MISRA-compliant solution since bitwise operations on signed integers have implementation-defined behavior. This solution definitively violates Rule 10.1. As you said ~0 is different than ~0U, 0xffffffffU, and 0xffffffff, so using ~0 means changing the semantics of the code: this is not the aim of the patch. -- Simone Ballarin, M.Sc. Field Application Engineer, BUGSENG (https://bugseng.com <http://bugseng.com>)
